#!/bin/bash

# Program:
#    You input your demoilization date, I calculate how many days 
#    before you demobilize.
# History:
#    2015/08/25    wxb    First release

echo "This program will try to calculate :"
echo "How many days before your demobilization date..."

read -p "Please input your demobilization date (YYYYMMDD ex>20150825): " date2

date_d=$(echo $date2 | grep '[0-9]\{8\}') 
if [ "date_d" == "" ]; then
    echo "You input the wrong date format..."
    exit 0
fi

declare -i date_dem=`date --date="$date2" +%s`
declare -i date_now=`date +%s`
# There are no space between ( and (
declare -i date_total_s=$(($date_dem - $date_now))
declare -i date_d=$(($date_total_s/60/60/24))
if [ "$date_total_s" -lt "0" ]; then
    echo "You had been demobilization before: " $((-1*$date_d)) " ago"
else
    declare -i date_h=$(($(($date_total_s-$date_d*60*60*24))/60/60))
    echo "You will demobilize after $date_d days and $date_h hours."
fi
